Thanks for the replies this cleared up a lot.
Right I think I will be using Dovecot for IMAP (less clients) with index files and keep on using Courier for POP3 (most clients). According to my tests this works OK on the same mailbox.
Cheers,
Jan
-----Oorspronkelijk bericht----- Van: Timo Sirainen [mailto:tss@iki.fi] Verzonden: vrijdag 8 februari 2008 17:58 Aan: Jan van den Berg CC: Dovecot Mailing List Onderwerp: Re: [Dovecot] Expected size of index-files?
On Fri, 2008-02-08 at 17:45 +0100, Jan van den Berg wrote:
I'm scared to use (index) files that go sort of unnoticed (it's not calculated in the maildirsize file) and can potentially grow with no limit.
Only some truly badly behaving clients can cause them to grow infinitely. This would require the client to fetch/search more and more unique message headers. For example field1, field2, field3, .. field1000. I don't think this is worth worrying about, although I guess I should add code to prevent this. Added to TODO.
But I am also curious what ":INDEX=MEMORY" will do with 100k users. How much MB RAM will one IMAP session on average take?
The problem isn't how much memory it'll take. It's that Dovecot may use a lot more disk I/O because it has to read and parse messages to find some data instead of doing a couple of small reads from cache file to get the same data.
The memory usage is actually less without indexes, because then no fields are ever cached and the space used by dovecot.index.cache isn't mapped to memory.
And will this be removed from memory (or stay cached) when an IMAP session is closed?
Operating system's buffer cache may still contain all the message files' contents that were read during the session (which may have been avoided with indexes on disk), but that's all.